1. Field
Embodiments relate to a chamber-status monitoring apparatus and a method capable of simultaneously measuring the statuses of a plurality of chambers in a semiconductor fabrication process by use of a multi-input optical emission spectroscope.
2. Description of the Related Art
Typically, in the semiconductor fabrication process, a plasma etching process is utilized to remove or etch material patterned on a silicon substrate. For example, once a semiconductor substrate with an overlying patterned, protective layer is positioned within a chamber, an ionizable, dissociative gas mixture is introduced within the chamber at a pre-specified flow rate, while a vacuum pump is throttled to achieve an ambient process pressure. Thereafter, plasma is formed when a fraction of the gas mixture in the chamber is ionized by heated electrons, e.g., heated via either inductive or capacitive power supply. Moreover, the heated electrons serve to dissociate some species of the gas mixture and create reactant specie(s) suitable for the exposed surface etch chemistry.
Once the plasma is formed, selected surfaces of the substrate are etched by the plasma. The process is adjusted to achieve optimal conditions, e.g., an appropriate concentration of desirable reactant and ion populations to etch various features in the selected regions of substrate. The etched materials, e.g., the substrate or layers thereon, may include silicon dioxide (SiO2), low-k dielectric materials, poly-silicon, and silicon nitride. As the feature size is reduced and the number and complexity of the etching process steps used during integrated circuit fabrication is increased, the requirements for tight process control become more stringent. Consequently, real time monitoring and control of such processes becomes increasingly important in the semiconductor fabrication.
For example, one such monitoring technique may include endpoint detection, which determines timely completion of an etching step or process. In particular, endpoint detection refers to a detection of a completed etched feature or to an instant in time when the etch front reaches an etch stop layer. If the endpoint detection is inaccurate, severe under-cutting of features may occur due to over-etching, or partially completed features may result due to under-etching. As a result, poor endpoint detection could lead to devices of poor quality that are subject to increased risk of failure. Therefore, accurate and precise completion of an etching process is important in the semiconductor fabrication.